NCS NUS example - bigger buffer

Question

Hi,
I have two Nordic BLE devices, one nrf52-DK that has peripherial_uart application and nrf52840-DK that has central_uart application. This works well, but the thing I need to change is buffer size (from central to peripheral) which is set to 20 bytes by default. I need it to be much bigger, around 500 bytes. This is because I need it to send more data et once, and not 20 my 20 bytes.

I have managed to change this on the peripherial_uart application size in the Kconfig file so now buffer on the peripheral side is 1024. On the central size I have tried changing buffer size in the main file: #define UART_BUF_SIZE 20, from 20 to something bigger, but I get a fault when try to send data that is bigger than 20 bytes.

What else needs to be done besides just increasing buffer size on both applications? I suppose there is something with BLE or NUS?

I am using Ubuntu 18.04LTS and NCS v1.2.0

Best regards,
Vojislav.

Simon · Accepted Answer

I was able to send 1000 bytes by doing the following: 
 
 In ncs
rf\samples\bluetooth\central_uart\prj.conf set these: 
 
 CONFIG_BT_L2CAP_TX_MTU=1024
CONFIG_BT_L2CAP_RX_MTU=1024
CONFIG_BT_RX_BUF_LEN=1024 
 
 In ncs
rf\samples\bluetooth\peripheral_uart\prj.conf set these: 
 
 CONFIG_BT_GATT_NUS_UART_BUFFER_SIZE=1024
CONFIG_BT_RX_BUF_LEN=1024
CONFIG_BT_L2CAP_TX_MTU=1024
CONFIG_BT_L2CAP_RX_MTU=1024 
 
 In in ncs\zephyr\subsys\bluetooth\host\att_internal.h , set BT_ATT_DEFAULT_LE_MTU to 1024 
 
 In ncs
rf\samples\bluetooth\central_uart\src\main.c set UART_BUF_SIZE to 1024

If you're going to send data chunks of size 1024, you may have to set the buffers a little bigger, due to overhead and so on. 
 Best regards, 
 Simon

NCS NUS example - bigger buffer

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